Alternative X-ray filters for an intra-oral digital radiographic system

Abstract

Objective: The aim of this study was to evaluate the effect of the modulation of the radiation spectrum with the use of alternative X-ray filters in the quality of intra-oral digital images from storage phosphor plates. Methods: The radiographic exposures were performed in a GE 1000 X-ray machine (General Electric Co., Milwaukee, WI), operating at 65 kVp, 10 mA, 40 cm focus receptor distance using three different exposure times: 0.05 s, 0.16 s and 0.35 s. The control filter (GC) was 100% aluminium (Al) with a thickness of 1.5 mm. The tested filters were: G1, 97% Al and 3% copper (Cu) with 1.47 mm thickness; G2, 96% Al and 4% Cu with 1.53 mm thickness; G3, 95% Al and 5% zinc (Zn) with 1.56 mm thickness; G4, 98% Al and 2% Zn with 1.5 mm thickness; and G5, 95% Cu and 5% Zn with 1.6 mm thickness. For formation of the image, a 12-step Al wedge (each step with increments of 1 mm in thickness) was radiographed 10 times. Pixel values measured in digital images were converted into optical density (OD). Results: All replicates showed OD with high reproducibility (r . 0.95) for all exposure times and tested filters. In comparison between filters, statistically significant differences in density (p , 0.05) were observed. The OD curve of the G5 filter in all exposure times and G3 filter in an exposure time of 0.05 s showed changes in shape (p , 0.05). Conclusions: Excluding the G5 filter, all others tested filters can be used as a substitute for GC without losses in image quality.

Evaluation of low-contrast perceptibility in dental restorative materials under the influence of ambient light conditions

“…5,24 However, an adjustment in characteristic curves of the images can occur, because photostimulable phosphor digital systems use a histogram equalization algorithm (automatic range control) during image acquisition, which corrects the contrast from the images. 24 Histogram equalization algorithm is very important, because these systems own high latitude, which makes it possible to deviate from the optimal exposure and continue generating images that are subjectively very similar. However, it cannot be regarded as an advantage owing to the risk of overexposing the patient to high exposures or a lack of diagnostic quality with noisy images in low exposures.…”

Influence of Radiopacity of Dental Composites on the Diagnosis of Secondary Caries: The Correlation Between Objective and Subjective Analyses

“…10 Another important factor to be considered is the pureness of the Al wedge used in the conversion unit, considering the different alloys used as potent filtering objects for radiation; any alloy changes, related to a contaminating agent with a higher or lower atomic number, can significantly modify the radiation spectrum and result in a different image. 16 In the current study, the Al wedge had 99.8% purity, similar to the alloy used in the tube of the X-ray machine, such as Al X-ray filters. 16 However, another important factor is that the 12 steps of the Al wedge used in the current study are 1 mm thick.…”

“…16 In the current study, the Al wedge had 99.8% purity, similar to the alloy used in the tube of the X-ray machine, such as Al X-ray filters. 16 However, another important factor is that the 12 steps of the Al wedge used in the current study are 1 mm thick. This could result in a model of regression with a good fit, which could perhaps not be obtained if each step was thicker.…”

“…15,17 Clinically, there are more challenges, because in addition to the characteristics of the carious lesion, there are also the inherent troubles associated with the radiographic image 2,3 because caries detection is possible when demineralization has occurred in more than 40% of tooth tissue. 18 The use of secondary caries-like lesions for analysis of observers' performance has been previously applied, 2,12,13,16 and the size of the cavity bears an influence in this performance. 12 In this study, a same-sized bur 12 was used in repeated specimens because the perceptive reliability was an important factor under consideration.…”

Evaluation of the Radiopacity of Contemporary Luting Cements by Digital Radiography

“…Any alloy changes related to a contaminating agent with a higher or lower atomic number, can significantly alter the radiation spectrum and lead to a different image. 27) Some authors have emphasized the importance of dental tissue cuts as a secondary standard, and expressed the relative radiopacity of materials, enamel, and dentin as the aluminum equivalent values (in mm). 9,11) The use of dental tissue cuts as a secondary standard is helpful for evaluating materials with radiopacity between dentin and aluminum with the same thickness, such as RelyX Unicem Clicker.…”